Kill the Spider King. This is just a tutorial quest. They even provide some computer-driven companions that will kill the spiders for you even if you do nothing to help.

Opening Dialogue

Robin says, "I've just found some Ravine Spiders in my yard. My little helpers are trying to defeat them. However, I'm very worried about them. They could get hurt! Can you do me a favor? They are just behind the fence! Please!"

Closing Dialogue

I wasn't mistaken! You have true hero potential! I'll prepare some rewards for you. You can pick whichever one you like best. I hope that it will be helpful on your journey.

Heroes like you can help the citizens in Candara! There is a settlement not far from here. Let my Mount give you a ride!